Traditionally, primarily pickup trucks were used in construction and other work related activities. However, truck popularity, especially the new miniature pickup trucks, has increased dramatically in the last decade. These new light trucks are inexpensive to buy, versatile, practical and have become the vehicle of choice for many individuals for both work related and recreational activities.
However, in spite of the many positive attributes of pickup trucks, fuel inefficiency remains a major drawback. Pickup truck fuel inefficiency is inherently part of the design associated with high profile vehicles having various blunt surfaces and other features that are aerodynamically inefficient. One of the most aerodynamically impaired features is the truck bed, especially when the tailgate is closed in its upright position. In the upright position the tailgate creates a wall at the rear of the truck over which the air must travel when the vehicle is in motion. Air hitting the tailgate creates aerodynamic drag that results when moving air hits a blunt object, restricting its ability to flow smoothly around or over the object.
As an object moves through a fluid such as air or water, its forward progress is determined by the amount of thrust (pushing or pulling power) minus drag. Drag results when the fluid medium which the object is moving through strikes a surface (boundary front) on the object. The greater the drag, the more thrust that is required for an object to accelerate or maintain a set speed as it moves through the fluid medium. For example, as air pushes against a solid vertical surface (the boundary front), such as a tailgate, it strikes the boundary front at a right angle (90.degree.). This in turn creates maximum drag as the air begins to swirl rapidly at the boundary front creating turbulent air. The turbulent air acts like miniature cyclones (vortexes) pulling more air into its center and holding the air against the boundary front, thus restricting its flow over the object. Consequently, the turbulent air must force its way over the boundary being impeded by the boundary itself and the turbulent air vortexes.
Aerodynamic drag can be reduced by eliminating the boundary front, reducing the angle of attack at the boundary front or increasing the rate at which air moves past the boundary. In many, if not most cases, the boundary front is a necessary or desirable part of the object and its elimination is not an option. Therefore, means of causing air to move more efficiently over the object must be considered first.
One means of increasing air flow over or around a boundary is to reduce the angle of attack between the moving air front and the boundary front. Reducing the angle of attack at the boundary front allows more air to freely pass over the boundary, reducing vortex generation and drag. However, merely reducing the angle of attack, while an improvement over a vertical surface, is an insufficient means of maximizing aerodynamic efficiency. Therefore, for minimum drag and maximum aerodynamic efficiency it is also necessary to promote or induce the smooth, laminar flow of air across the boundary's surface.
Laminar air flow results when air flows over a surface in a substantially parallel fashion. For example, imagine air rushing towards a boundary front as a series of parallel lines. As these parallel lines of air strike a boundary front they are deflected such that the parallel lines cross each other, forming vortexes. However, if a boundary could be created that would promote or induce the flow of air over its surface in substantially parallel lines, vortexes would be minimized and airflow would be substantially less impeded. This in turn would substantially decrease drag and increase performance efficiency of an object by reducing the energy required to generate thrust.
Various attempts have been made to alleviate the aerodynamic deficiencies of the truck bed. For instance, truck owners leave the tailgate open or remove the tailgate entirely. While leaving the tailgate open may alleviate drag associated with the tailgate in the closed position, the open tailgate may cause an increase in lift, creating vehicle instability at high speeds. Furthermore, if the tailgate is left open, its appearance may be marred by rocks and road debris. Additionally, smaller items cannot be stored in the truck bed since the items may either slide around the truck bed, which may damage the items, or they may fall out of the truck bed when the vehicle is in motion.
Mesh-type netting is another attempt to improve the aerodynamics of the truck bed. The mesh-type netting allows the air to flow through the rear of the truck partially alleviating aerodynamic drag. A drawback to the mesh-type netting is the tailgate must be removed from the truck and stored. Furthermore, smaller items may slide around in the truck bed and fall out when the vehicle is in motion through the open mesh netting. Moreover, smaller items cannot be securely stored and remain exposed to the elements. Additionally, the mesh-type netting may not be visually appealing to many truck owners.
In addition to the aerodynamic deficiencies in conventional truck bed design, there is a lack of storage space to hold smaller items such as groceries and work tools. Normally these items may be strewn about the bed when the truck is in motion. Furthermore, smaller items may be damaged while exposed to the elements such as rain, hail, sleet, or snow. Traditionally, a storage box is placed in the truck bed adjacent to the truck cab. Although the storage box placed behind the truck cab reduces storage problems, they are difficult to access, requiring the user to reach over the side of the truck, or climb into the truck bed to access to the storage box. Furthermore, traditional storage boxes do not alleviate the aerodynamic deficiencies of the truck bed and add considerable weight to the vehicle, further reducing fuel efficiency associated with conventional tailgate design.
One means of reducing drag and increasing truck utility has been the placing of a storage box adjacent to the tailgate. These storage boxes are triangularly-shaped, having a sharp linear incline from the top of the tailgate to the truck bed such that a right triangle is formed. Although it may seem that an inclined surface would reduce air resistance, the inventors of the present invention surprisingly found that the inclined surface still creates turbulent airflow as a result of the abrupt angle of impact between the moving air front and the boundary's linear surface. Consequently, aerodynamic resistance is only partially alleviated and fuel inefficiency remains high as previously described. Furthermore, this design reduces truck bed length significantly limiting the truck's overall utility for hauling oversized objects. Therefore, it would be a significant advance in truck design if an aerodynamic device were developed for pickup truck beds that significantly reduced aerodynamic drag at the tailgate and induced laminar air flow. Moreover, it would be an even greater advance if a laminar air inducing aerodynamic device for the pickup truck also increased the truck's utility by integrating within it a versatile storage space in addition to increasing overall fuel efficiency.